NationalNational HydrologyHydrology committeecommittee ofof AfghanistanAfghanistan (NHCA)(NHCA) SedimentationSedimentation inin ReservoireReservoire

OCt.2007

Prof. Mohammad Qasem Seddeqy KPU ﺑﺴﻢﺑﺴﻢ اﷲاﷲ اﻟﺮﺣﻤﻦاﻟﺮﺣﻤﻦ اﻟﺮﺣﻴﻢاﻟﺮﺣﻴﻢ

وﺟﻌﻠﻨﺎﻡﻦوﺟﻌﻠﻨﺎﻡﻦ اﻟﻤﺎءﮐﻞاﻟﻤﺎءﮐﻞ ﺷﺊءﺷﺊء ﺣﯽﺣﯽ

وازواز ﺁبﺁب هﺮهﺮ ﭼﻴﺰﯼﭼﻴﺰﯼ رازﻥﺪﻩرازﻥﺪﻩ ﮔﺮداﻥﻴﺪیﻢﮔﺮداﻥﻴﺪیﻢ ﺱﻮرﻩﺱﻮرﻩ اﻥﺒﻴﺎاﻥﺒﻴﺎ ایﻪایﻪ 3030

ClassificationClassification ofof RiversRivers accordingaccording toto thethe topographytopography ofof thethe riverriver basinbasin

¾ UpperUpper reachesreaches inin thethe hillyhilly regionregion ¾ LowerLower reachesreaches inin thethe alluvialalluvial plainplain

RiversRivers onon alluvialalluvial plainsplains maymay bebe broadlybroadly classifiedclassified inin toto threethree types:types: 1. TheThe meanderingmeandering typetype 2. TheThe aggradingaggrading typetype 3. TheThe degradingdegrading typetype

SedimentSediment isis fragmentalfragmental material,material, primarilyprimarily formedformed byby thethe physicalphysical andand chemicalchemical disintegrationdisintegration ofof rocksrocks fromfrom thethe earthearth crust.crust.

TheThe processprocess ofof movingmoving andand removingremoving fromfrom theirtheir originaloriginal sourcesource oror restingresting placeplace isis calledcalled erosionerosion WhyWhy aa goodgood understandingunderstanding ofof sedimentsediment transporttransport processesprocesses isis indispensableindispensable

1.1. MorphologicalMorphological boundaryboundary conditioncondition forfor designdesign ofof HydraulicHydraulic structurestructure andand riverriver trainingtraining worksworks 2.2. SedimentationSedimentation inin reservoirsreservoirs 3.3. SedimentSediment problemsproblems atat IntakesIntakes 4.4. EnvironmentalEnvironmental ImpactImpact assessmentassessment OriginOrigin andand typestypes ofof SedimentSediment

¾¾ CohesiveCohesive ¾¾ NonNon CohesiveCohesive CohesiveCohesive sedimentsediment –– thethe physicalphysical-- chemicalchemical interactioninteraction betweenbetween particlesparticles playsplays aa significantsignificant role.role. NonNon CohesiveCohesive sedimentsediment –– therethere isis nono physicalphysical andand chemicalchemical interactioninteraction betweenbetween individualindividual particlesparticles ..

SedimentSediment ControlControl PlanPlan Q

Control Point （Q+A-B)*α A B

C E D Target Area

¾ E=(Q+A - B)(1 -α） - C - D SedimentSediment ControlControl PlanPlan

¾ E=(Q+AE=(Q+A -- B)(1B)(1 --αα）） -- CC -- DD

z E : Design allowable sediment discharge

z Q : Design sediment discharge at the design control point of the upstream end of the subject sub-basin

z A : Design sediment production

z B : Design reduction of sediment production

z α : Ratio of volume of channel sediment mitigation

z C : Design reduction of sediment discharge

z D : Design mitigation volume of sediment discharge SedimentSediment ControlControl DamDam ¾¾ FunctionFunction 1:1: ToTo StabilizeStabilize HillsideHillside SlopesSlopes Scouring force becomes less than before； Shallower in depth, Slower in velocity SedimentSediment ControlControl DamDam ¾¾ FunctionFunction 11 ToTo ReduceReduce SedimentSediment DischargeDischarge Sediment Capacity for Flood Period

Initial Sediment Capacity SedimentSediment ControlControl DamDam ¾¾ FunctionFunction 2:2: ToTo MitigateMitigate StreambedStreambed ErosionErosion byby mildermilder bedbed--slopeslope withwith StepwiseStepwise DamsDams L

1 m m>n h 1 n L=((m*n)/(m - n))*h SedimentSediment ControlControl DamDam ¾¾ FunctionFunction 3:3: ToTo MitigateMitigate SedimentSediment RunoffRunoff Design Sedimentation Line to Cover the Unstable Sediment Deposition

Unstable Sediment Deposition

3D VIEW OF KABUL RIVER BASIN

Naghlu Kabul dam

Oulet basin 3D View of Alingar River Basin

Darunta Dam Other view from agriculture land of Gulbahar –Panjsheer desert 3D view of Sorobi and Naglu dams

Naghlu dam

Sorobi dam 3D View of from Kunar River

Kunar river Pakistan

Darunta dam 3D View of Darunta Dam

Darunta dam 2002-09- : Date Landsat 7 satalite 22 3D View of Panjsheer river Basin

Gulbahar desert

Naghlu dam

Darunta dam Darunta Reservoir 24 years ago

1979-06- : Date Landsat 3 satalite 20

••SedimentationSedimentation

¾ IntensiveIntensive soilsoil erosionerosion hashas beenbeen causingcausing rapidrapid sedimentationsedimentation ofof reservoirsreservoirs withwith anan importantimportant lossloss ofof irrigationirrigation lands,lands, powerpower generationgeneration capacitycapacity andand lifelife timetime ofof reservoirsreservoirs

¾ AfganistanAfganistan isis facingfacing annuallyannually withwith 150150 millionmillion m3m3 sedimentationsedimentation inin thethe reservoirsreservoirs andand 400400 millionmillion m3m3 sedimentationsedimentation toto downstreamdownstream ofof damdam reservoirsreservoirs andand irrigationirrigation networksnetworks CausesCauses ofof sedimentationsedimentation

¾ Desertification 1. Continued deforestation from logging and fuel wood needs : In South,east and northeast of Afghanistan. 2. overgrazing:The grazing lands used by Kochis (nomads)have been dried out due to the lack of sufficient rainfalls & converting to cultivable land causing considerable reduction in livestock and livelihood. 3. Destroying land covers bush used for fuel wood 4. Soil erosion due to flood and wind 5. Unsustainable agriculture :Salinization of soil ,over use of agricultural inputs. 6. Drought :Started in 1969,getting up to a critical status in 1997- 2002 ,causing hydrological circulations of the soil ¾¾ LackLack ofof riverriver mangementmangement andand trainingtraining workwork ¾¾ LandLand useuse ¾¾ steepsteep drainagedrainage basinbasin slopesslopes andand reliefrelief ¾¾ highhigh rainfallrainfall magnitudesmagnitudes andand frequenciesfrequencies ¾¾ LackLack ofof ReservoirReservoir maintenancemaintenance ExtensiveExtensive destructiondestruction ofof forestforest overover thethe pastpast 2525 yearsyears SedimentationSedimentation andand erosionerosion problemsproblems affectaffect thethe followingfollowing sectors.sectors. ¾ Health(drinkingHealth(drinking waterwater ,, domesticdomestic )) ¾ SocietySociety ¾ Economy(Economy(WaterWater supply,Irrigation,Hydropower,Maintenancesupply,Irrigation,Hydropower,Maintenance andand operationoperation ofof Reservoir,Reservoir,NavigationNavigation,,FloodFlood ProtectionProtection,,FisheryFishery )) ¾ EnvironmentEnvironment FlashFlash floodingflooding isis aa directdirect consequenceconsequence ofof landland covercover degradationdegradation inin BalkhBalkh riverriver 2626 March,March, 20032003 SedimentSediment depositiondeposition intointo reservoirsreservoirs hashas severalseveral majormajor detrimentaldetrimental effects.effects. ¾ Loss of storage capacity. ¾ Damage to or impairment of hydro equipment. ¾ Bank erosion and instabilities. ¾ Downstream channel modification. ¾ Reduced downstream suspended sediment load. ¾ Upstream aggradations. ¾ Effect on water quality. ¾ Effect on waste assimilation. ¾ Effect on navigation and recreation. ¾ Effect on aquatic life. PlansPlans forfor mitigationmitigation ofof erosionerosion andand sedimentationsedimentation

¾ For urgently Dredging,Dredging, SubSub cut,cut, emptyempty washingwashing ¾ Reforestation and plantation for land covering long term ¾ PreparationPreparation ofof NationalNational StrategyStrategy andand policypolicy forfor erosionerosion andand sedimentsediment mitigation.mitigation. ¾ UseUse waterwater resourceresource potentialpotential inin thethe countrycountry throughthrough rainrain andand floodflood waterwater harvesting,harvesting, constructionconstruction ofof small,small, medium,medium, andand largelarge depressions,depressions, poolspools andand damsdams forfor floodflood controlcontrol andand preventionprevention ofof erosionerosion .. ¾ ConstructionConstruction ofof protectiveprotective structuresstructures alongalong riverriver wherewhere slidingsliding maymay occur.occur. ImmediateImmediate ResponseResponse ¾ GoodGood riverriver managementmanagement :includes:includes sedimentsediment andand floodplainfloodplain managementmanagement ¾ NationalNational EmergencyEmergency EmploymentEmployment Program,Program, NationalNational SolidaritySolidarity ProgramProgram andand NationalNational HydrologyHydrology programprogram ofof AfghanistanAfghanistan (NHCA),(NHCA), BasedBased DevelopmentDevelopment programprogram andand otherother NationwideNationwide programsprograms areare contributingcontributing toto ErosionErosion andand sedimentationsedimentation reliefrelief ¾ EmergencyEmergency RehabilitationRehabilitation IrrigationIrrigation ProjectProject (Hydraulic(Hydraulic structures)structures) ¾ IntermittentIntermittent meetingsmeetings byby UNUN andand GovernmentalGovernmental andand wellwell--knownknown nonnon--GovernmentalGovernmental AgenciesAgencies forfor assessingassessing responseresponse andand coordinationcoordination regardingregarding erosionerosion andand sedimentationsedimentation managementmanagement andand capacitycapacity BuildingBuilding

conclusionconclusion

¾ The principal reservoirs of Afghanistan are rapidly losing their storage capacity and day by day exacerbated because of high rates of sediment influx and accumulation. ¾ The factors that promote sedimentation in the reservoirs include land use, steep drainage basin slopes and relief, and most importantly, high rainfall magnitudes and frequencies and lack of maintenance due to prolong war. ¾ connecting reservoirs at high elevations with those at lower elevations, results in an increased drainage area and available water. As the upstream reservoirs fill with sediment, however, the bottoms reach the outlet structures and sediment is bypassed into the lower reservoirs, accelerating the sedimentation rates in these impoundments. ¾¾ ReservoirsReservoirs withwith smallsmall drainagedrainage areasareas lossloss storagestorage capacitycapacity atat aa fasterfaster raterate thanthan reservoirsreservoirs withwith largerlarger basins,basins, especiallyespecially inin developeddeveloped basins.basins. ¾¾ InIn reservoirsreservoirs withwith largelarge basinsbasins however,intensehowever,intense rainfallrainfall inin aa shortshort periodperiod cancan transporttransport largelarge amountsamounts ofof sedimentsediment intointo thethe reservoirs,reservoirs, rapidlyrapidly depletingdepleting theirtheir storagestorage capacity.capacity. ¾¾ EffortsEfforts toto significantlysignificantly increaseincrease thethe overalloverall waterwater resourcesresources byby simplysimply buildingbuilding moremore damsdams overover timetime ,, isis provingproving toto bebe ineffectiveineffective on a long-term basis. ThankThank youyou forfor attentionattention